Method of blasting



Jan. 3, 1967 T. z.BA1 ETAL METHOD OF BLASTING .v

Filed July 2l, 1965 zot d@ ZQEE ,Tsw @Emi mozoumj ooo@ wmzowj @comwnomzzw mozmnomw msi m 050m@ N 505 m505 llwmjo NIV $.61 N|Y L $.51 wmTeoow @55mg wsoomm @50mg Tem eoom smv 350002 350%: Eem@ 268B @ENE @soos25mg A260; www m6 wm@ w m5 wm@ mm@ m@ @o no 253mg 758mm@ Tsomwwu Tsooom.wsom $628 .29 :E032 eooo: me om@ 320mm@ @55S meco@ Econ; w59 i@ m5 m6 8m0 u H2552 @22 memt Engl @CSE 352m@ eomt Gem 3&3.: 25ms @SMS2 39000@E508 @soos GEOS mm@ Q mm@ 5 m3 Nm@ m0 m@ No INVENTORS Thomas Z. BollUnited States Patent Oiice Patented `Fain. 3, 1967 3,295,445 METHOD FBLASTING Thomas Z. Ball, New Ringgold, and Edwin G. Brown, Thornton,Pa., assignors to Atlas Chemical Industries, Inc., Wilmington, Del., acorporation of Delaware Filed July 21, 1965, Ser. No. 473,597 3 Claims.(Cl. 102-23) This invention relates to a method of detonating a largenumber of explosive charges in a desired sequence. More particularly, itrelates to a method of blasting utilizing a multiplicity of chargesarranged in a plurality of groups which are denoted sequentially bymeans of delay detonators in such la manner so that groups of chargesnot yet red are initiated before proximate charges in adjacent groupsare tired.

In blasting oper-ations utilized in mining it is often desirable to re alarge number of shots along a face o-r wall being mined in .a -denitesequence at very close intervals. Generally, this technique is desired'because it usually results in blastin-g in which Ibetter breaking ofthe tace is `achieved than whe-n larger but less numerous explosivecharges are used or when all of the charges placed in the face arecaused to fire at the same instant.

In the long wall method 4of mining a typical face to be blasted may beseveral hundred feet long. To satisfactorily break-up such a face theexplosive charges to be used are placed in holes arranged in rowsrunning along the length of the face. For example, holes may be arrangedin vertical rows so that each hole in a given row is approximately threefeet from the next hole and the vertical rows are spaced approximatelythree feet apart. Thus with a face of about 300 feet long and six feethigh there will be about 300 blasting holes containing an equal numberof explosive charges. In blasting such a face it is advantageous todetonate the entire face as a single round but it is desirable to have aminimum number of detonations (preferably one) occurring `at any giveninstant in order to minimize damage to surrounding roofs due to iiyingmaterial and/or vibrations and to produce a good breaking of the facebeing blasted. Therefore, in essence, it is desirable to have a methodof shooting a large number of charges over a relatively short period insuch a manner so that only one charge or a few charges is shot at anygiven instant but such that all of the charges are shot Within a periodof a few seconds or longer in a desired sequence. It is important in theblasting of a face, as ydescribed above, that the various charges bearranged and tired in a manner so that the leads running to chargesadjacent to those fired a-re not broken by flying material from chargespreviously fired.

An object of this invention is t-o provide a method of detonating alarge number of explosive charges in close order in a desired sequence.

Another object of this invention is to p-rovide a method of blastingwith a large number of explosive charges through the use of delay tiringdetonators arranged in groups whereby only one explosive charge is firedat any given instant and whereby the groups of charges not yetA firedare initiated sequentially before proximate charges in adjacent groupsare tired.

Other objects of this invention will be obvious to those skilled in theart in view of the following description.

The method of the present invention involves blasting wherein amultiplicity of changes is detonated in a desired sequence by delaydetonators. The present method comprises initiating del-ay tiringdetonators in separate groups so that the charges in a first group areinitiated at one time while charges in adjacent groups are initiated ata later time, but prior to detonation of any charge in said rst groupwhich has a field of execution inclusive of any charge of said adjacentgroup. However, according to the present method, the delay betweeninitiation -and ring of Iany charge of any such adjacent group withinsuch iield of execution is such that said charge of such adjacent groupdetonates after ldetonation of the charges having such a fieldofexecution.

In the present invention, the desired firing sequence is achieved -byutilizing a series `of varying delay firing detonators. Suitably, eitherthe fuse or electric type of blasting cap may be used in the presentmethod. The delay tiring electric blasting cap-s which lare used inaccordance with the present invention are such that can be initiated andwill lire over a period of time. -Delay tiring electric lblasting capsare known to be comprised of the various customary elements ofconventional electric blasting caps, 'and in addition a train ofIdeilagrating material located bet-Ween the ignition element and thedetonating charges in the blasting caps. The train of defagratingmaterial in the cap produces the desired delay in the firing of the capafter its ignition. The period of dela-y after ignition and beforefiring is varied according to the length and speed of burning of thedelay train in the yblasting cap. In the utilization of the p-referredembodiment of this invention it is desirable to use delay tiringelectric blasting caps which possess delay periods of from a fraction ofone second to about 7.5 seconds or longer and which vary between eachother at intervals between about 5 and about 125 milliseconds.

The delay iiring of the lfuse-type caps is obtained and varied by usingvarying types and lengths of safety fuses. In roperation such fuses areproperly connected to a trunk line of ignition cord, such as sold underthe trademark Ignitacord `and manufactured by the Ensign-Bickford Co. ofSimsbury, Connecticut, which in turn is ignited by means of an electricstarter which is initiated Iby means of an electric multiple circuitswitch located in an area remote from the blasting site.

The blasting method of the present invention will be more readilyunderstood in view of the figure of the accompanying drawing whichillustrates an embodiment of the subject invention wherein delayelectric blasting caps are used in combination with an ele-ctric timedsequence switch. However, such a switch or timing device is notessential to carry out the present method. Such timing and initiationmay be done manually. The igure represents la vertical elevation of aface to be blasted. The C numbers sh-own in the ligure are theidentifying numbers of the detonators `as positioned within holes of theface illustrated. Due to the large number ort holes involved, the faceas illust-rated in the figure is shown in broken section. The numbers inparenthesis indicate the nominal delay time in millseconds of thevarious detonators utilized. The numbers in brackets indicate the sum ofthe delay time in milliseconds of the blasting cap used plus thesequence switch delay in initiating the particular group involved andrepresents the total time t-o elapse 'between detonation of the chargein Group 1 wherein Cap C1 is positioned and the detonation of the holeunder consideration in either Groups 2 or 3. Cap C1 is a standardinstantaneous electric blasting cap and not a delay firing blasting cap.

In the ligure, the first 36 holes are connected in an electrical circuitand connected to the iirst pair of terminals of a delay firing sequenceswitch. The next 24 holes are connected in a second circuit andconnected to a second pair of terminals of the same delay firingsequence switch. The 24 holes are connected in a third circuit andconnected to a third pair of terminals of the same delay tiring sequenceswitch. In practice the numbers of explosive charges and correspondinggroups could be in creased to a great number and the circuits could bein parallel, in series or in parallel-series. Additionally, the changesin the various gr-oups could be arranged in any suitable pattern. Thetiring pattern and times indicated in the gure are achieved by using thedelay electric blasting caps indicated with a sequence switch that isdesigned to furnish current to the successive pairs of terminalsindicated above at a time interval of about 3000 milliseconds. However,the `delay time of the sequence ring switch may 'be suitably varied tomeet the particular needs in regard to the area to be blasted and thenumber of blasting caps to tbe utilized.

AIn the illustration of the figure when the sequence ring switch isactivated, current is supplied instantaneously to the blasting caps inthe first 36 holes making up Group l. These caps will then lire in turnaccording to the delay train in the cap. Cap C36 in the igure has afiring delay of 3500 milliseconds. While the ydelay blasting caps in therst 36 holes are in the process of firing, the sequence switch is inmotion and at 3000 milliseconds cap C32 `of Group l tires and at thesame instant the sequence switoh supplies current to the second group ofblasting caps containing 24 blasting caps. Thus all of the caps in Group2 will be initiated before caps C33, C34, C35, and C36 of Group l fire.Similarly, this same process will Ibe 'repeated in 3000 millisecondintervals With each succeeding group, connected to the sequence switch.

According to the present method, all of the deonators of each succeedingcircuit or lgroup Will respectively receive their initiating currentprior to the firing of the proximate adjacent charges in each of therespective preceding igroups as shown in the gure. This precaution istaken to insure intiation of the caps in a group before the wiresleading to each succeeding group are exposed to breakage by rockmovement from nearby holes of the preceding group.

What we claim is:

1. In a method of blasting wherein a multiplicity of charges isdetonated at varying times by delay detonators, the improvement whichcomprises initiating the detonators in separate groups of charges sothat the detonators in a rst group are initiated at one time Whiledetonators in an adjacent group are initiated at a later time but priorto detonation of any charge in such rst group which has a iield ofexecution inclusive of any charge of such adjacent group, the delaybetween initiation 4 and tiring of a detonator of any charge of suchadjacent group Within such field of execution being such that saidcharge of such adjacent group detonates after detonation of the changehaving such iield of execution.

2. In a method of :blasting wherein a multiplicity of charges isarranged in a line and detonated sequentially along said line by meansof delay detonators, the improvement which comprises grouping saiddetonators in successive sections in such line of charges in separategroups, initiating a rst suclh group, and then later, but prior to thedetonation of any charge in such first group which has a eld ofexecution inclusive of any charge in the next adjacent group, initiatingthe said next adjacent group, the delay between initiating and ring of adetonator of any charge of said adjacent group within such eld ofexecution being such that said charge of said adjacent group detonatesafter detonation of the charge having such eld of execution.

3. A method of blasting comprising connecting a plurality of varyingdelay liring electric detonators in a multipilicity `of electricalcircuits in a preselected ring order, arranging each of said circuits ofdetonators in groups of vertical rows in a -face to be blasted,connecting each of said circuits to a time sequence ring switch,initiating a first circuit vby said time sequence firing switch, theninitiating the next adjacent circuit by means of said time sequencefiring switch so that the next adjacent circuit is initiated before thedetonation of any charge in such rst circuit which has a field ofexecution inclusive of any charge of said next adjacent circuit, thedelay between intiation and firing of a detonator of any charge of saidadjacent ycircuit within such a eld of execution being such that saidcharge of said adjacent circuit detonates after detonation of thecharges havin-g such eld of execution.

References Cited by the Examiner UNITED STATES PATENTS 12/1955 Colemah102-23 12/ 1955 Janelid 102-23

1. IN A METHOD OF BLASTING WHEREIN A MULTIPLICITY OF CHARGES ISDETONATED AT VARYING TIMES BY DELAY DETONATORS, THE IMPROVEMENT WHICHCOMPRISES INITIATING THE DETONATORS IN SEPARATE GROUPS OF CHARGES SOTHAT THE DETONATORS IN A FIRST GROUP ARE INITIATED AT ONE TIME WHILEDETONATORS IN AN ADJACENT GROUP ARE INITIATED AT A LATER TIME BUT PRIORTO DETONATION OF ANY CHARGE IN SUCH FIRST